does anyone know the carb pilot screw settings

I am used to working on bikes that tell you how many turns it is in the manual. 3 of my plugs look fine but one of them is running rich. I just want to set them all the same and leave it. I have a K&N filter. I took the bike for a ride today, it ran great for a little while than started backfiring and had no power. The same thing that happened in the past when I was working on it. I have spent countless hours playing with the pilot screw, anyone know hom many turns it is? thanks

 

Stock is 2.5 turns out....but you're not stock. The K&N filter is typically known to require a rejet.

 

all the plugs look exactly like http://www.ngksparkplugs.com/tech_suppo ... aqread.asp
the picture of Normal. except for the cylinder where the plug is fouled with oil. Also now that I have been riding it, it will not idle. very strange it did this before. I think I should just put a stock filter in. I have a foam UNI filter I will try it out see how it runs. thanks

 

I don't know "How many turns" ... Out.
I ColorTune.
Then, ... I measure the Depth to the Top of the Screw for "Future" Pre-sets.

I made a Tool.
A Wooden Golf Tee.
Cut the pointy-end off, ... Flush & square.
Use a Precision Ruler:
Scribe a Line around the Tee ==> 11/32nds. (0.3438ins.) from the Bottom.

Use this Tool.
Set the Mixture Screws to this Depth ==> (Preset)
Make 2~5 Degree Adjustments from Preset
This is Chop "Neighborhood"

 

I couldn't find the golf tee method in the manual, so I tried here

 

How many miles on this bike? I think it needs its valve clearances checked and a carb service, quite honestly.

 

Black Spanker, hmm? Interesting question but at one point you stated that one plug is oil fouled? If that was my bike I think I would start with a compression test to see if their might be a inner reason for that oil fouled plug as in a bad ring ect.... Also from what I have read here it sounds like there may be a few things which you are behind on in the subject of overall maintenance (service) Oil fouling as I am sure you know comes from the crankcase rather than from the carburators? After the compression test and how the cylinder compares to the compression on the other 3 cylinders you might find some light on the subject. Also, the reply on how many miles you have on the bike that you might be in need of a valve adjustment I agree also. It's difficult to start diagnosing an engine if the engine has not had up to date maintenance performed on it because sometimes there is more than one problem contributing to the problem at hand. grunt007, 81' XJ750 SecaR, Mi. Also, with overhead valves possibly there could be an oil drain down on a valve in that cylinder, I'm not sure on these bikes how much of a posibilty that might be?

 

have not checked the valves yet.. but the compression test was good with all of the cylinders at 150 if I remember right. I will do another compression test. Also as Rick knows (we spent all of last summer rebuilding carbs. THANKS RICK!) the carbs are good. I followed his instruction and flushed out the carbs with brake cleaner before storing the bike.

 

thanks I will do another compression test

 

Check your valve clearances first.

 

The Golf Tee Method isn't in the Book!
Using a Golf Tee to set a Depth is, ... a Time-saving "Short-Cut"

The Process allows one to return the Pilot Mixture Screws to their Precise Location after removing them for Passageway Cleaning, or resetting a Preset prior to performing a Plug Chop.

The Golf Tee is simply an object that fits into the hole.
The Golf Tee gets altered and becomes a fabricated Tool.
Subsequent to its alteration the former Golf Tee becomes a Depth Gauge.
A Precision Instrument.

The Book says that the 750's Pilot Mixture Screw Preset is 2.5 Turns Out.
That information is, as we all know, absolutely incorrect.

 

Just joshing, Rick.

 

when I took my carbs off my seca 650 to clean them ( just bought it 2 weeks ago) the previous owner had all the jets screwed in tight. So after I clean everything, what do i set my jets to?

 

the distance from the top down doesn't mean anything, it's the distance from the bottom up that counts

 

What I did last worked pretty good...set them to where you can just feel them coming out through the hole....make sure you bench sync too.

After that, 2.5 turns out....that won't be right, but it will be a starting point.

Read post after post on how to tune your bike by ear.

Gently ride, watch for things like running temp, engine braking, response to the fuel enrichment, popping and backfiring from the exhaust, smoothness, throttle response, warm up time, and plug color.

Adjust in 1/32 of a turn increments until it suits you....ride gently until you confirm that you aren't running stupid lean.

Or buy a colortune....that would be a lot easier. And that's what I'm doing next.

Anybody want to loan me a colortune next weekend?

 

Precise Measurement of the Distance from the TOP ~ DOWN is a heck-of-a-lot more ACCURATE than a GUESS at how-far from the BOTTOM ~ UP.

I would have to say, ... and am quite sure others would agree, ... that the Value of >> 0.3438Ins. << Deep would allow EVERYONE who set the depth to that Value, ... To ALL be >>> P-R-E-C-I-S-E-L-Y <<< the SAME.

Not so accurate when you say:
Bottom the Screw
Turn it Out 2.5 Turns
Then a little-bit more than that.

 

Correct in every particular.

 

O.P. FWIW on my '81 750 Seca, I was at about 5.5 turns out with a K&N filter and stock jets (see last post in this ol' thread: http://www.xjbikes.com/Forums/viewtopic/t=1259 ) Might not be 'right' for yours, but perhaps a better starting point for you would be 4 turns out?

If you'll pre-pay for shipping both ways and a small contribution to my beer/scotch fund, sure. PM me.

 

Actually Rick, I have to disagree, though I have to admit mine might be the only exception. I have one carb that seems to be deeper than the rest. That's how I figured out the "from the bottom" method....not because I thought it was a better idea, but because for me it was the ONLY idea.

I didn't work too hard on figuring out why that one carb was different...the carbs were pretty clean when I got the bike so there was obviously some work done before....maybe it came off another bike, but except for that it all looks exactly the same. The pilot screws are the same size too.

The thread pitch is pretty reliable. For a bench tune, I really do think "x turns from flush" would be more accurate than either "top down" or "turns out" methods...but I have NO idea how many "turns from flush" is a good starting point.

 

hey rick so far youve been on the money as far as my bike goes, so please forvive the stupid noob questions-- first how many millimeters is 0.3438 inches? I just bought one of those machinist slide rules but its all metric. second is that measurement from the TOP of the pilot jet the BOTTOM of where it screws in? man Im trying follow here and I will get it I just need to be sure. And thanks for the homemade float set tool tip. Made it-- 17.5mm on the nose